PARK2 Depletion Connects Energy and Oxidative Stress to PI3K/Akt Activation via PTEN S-Nitrosylation.

PARK2 is a gene implicated in disease states with opposing responses in cell fate determination, yet its contribution in pro-survival signaling is largely unknown. Here we show that PARK2 is altered in over a third of all human cancers, and its depletion results in enhanced phosphatidylinositol 3-kinase/Akt (PI3K/Akt) activation and increased vulnerability to PI3K/Akt/mTOR inhibitors. PARK2 depletion contributes to AMPK-mediated activation of endothelial nitric oxide synthase (eNOS), enhanced levels of reactive oxygen species, and a concomitant increase in oxidized nitric oxide levels, thereby promoting the inhibition of PTEN by S-nitrosylation and ubiquitination. Notably, AMPK activation alone is sufficient to induce PTEN S-nitrosylation in the absence of PARK2 depletion. Park2 loss and Pten loss also display striking cooperativity to promote tumorigenesis in vivo. Together, our findings reveal an important missing mechanism that might account for PTEN suppression in PARK2-deficient tumors, and they highlight the importance of PTEN S-nitrosylation in supporting cell survival and proliferation under conditions of energy deprivation.

PRKN-linked familial Parkinson's disease: cellular and molecular mechanisms of disease-linked variants.

Parkinson's disease (PD) is a common and incurable neurodegenerative disorder that arises from the loss of dopaminergic neurons in the substantia nigra and is mainly characterized by progressive loss of motor function. Monogenic familial PD is associated with highly penetrant variants in specific genes, notably the PRKN gene, where homozygous or compound heterozygous loss-of-function variants predominate. PRKN encodes Parkin, an E3 ubiquitin-protein ligase important for protein ubiquitination and mitophagy of damaged mitochondria. Accordingly, Parkin plays a central role in mitochondrial quality control but is itself also subject to a strict protein quality control system that rapidly eliminates certain disease-linked Parkin variants. Here, we summarize the cellular and molecular functions of Parkin, highlighting the various mechanisms by which PRKN gene variants result in loss-of-function. We emphasize the importance of high-throughput assays and computational tools for the clinical classification of PRKN gene variants and how detailed insights into the pathogenic mechanisms of PRKN gene variants may impact the development of personalized therapeutics.

Inhibiting Pink1/Parkin-mediated mitophagy enhances the anticancer effects of quercetin in hepatocellular carcinomaf.

Quercetin, a naturally occurring flavonoid, has been investigated for its potential anti-cancer effects in various types of cancer, including hepatocellular carcinoma (HCC). However, its suppressing effect on reactive oxygen species (ROS) production might limited its anti-cancer effects. In this study, we aimed to explore the interplay among quercetin, mitochondrial dynamics and mitophagy and whether mitophagy-inhibition synergistically enhances the anti-tumor effects of quercetin. Huh7 and Hep3B cells were utilized for in vitro and in vivo studies. Results showed that quercetin treatment significantly increased the expression of mitochondrial fusion genes (MFN1 and MFN2) and decreased the expression of fission genes (DRP1 and FIS1) in Huh7 and Hep3B cells, leading to a more fused and elongated mitochondrial network. Quercetin upregulated the expression of key mitophagy regulators, PINK1 and PARK2, and enhanced the colocalization of mitochondria with lysosomes, indicating increased mitophagy. Knockdown of PINK1, PARK2, or SIRT1 attenuated quercetin-induced mitophagy and reduction of intracellular ROS levels. Quercetin treatment upregulates SIRT1 expression, which subsequently enhances PINK1 and PARK2 expression in Huh7 and Hep3B cells. In vivo experiments using Hep3B xenograft models revealed that the combination of quercetin with the mitophagy inhibitor hydroxychloroquine or SIRT1 knockdown significantly enhanced the anticancer effects of quercetin, as evidenced by reduced tumor size and weight, increased necrosis and apoptosis, and decreased proliferation in tumor tissues. These findings suggest that quercetin-induced mitochondrial fusion and Pink1/Parkin-dependent mitophagy may negatively influence its anti-cancer effects in HCC. Targeting mitophagy may enhance the therapeutic potential of quercetin in HCC treatment.

Pathogenesis of Parkinson's disease: from hints from monogenic familial PD to biomarkers.

Twenty-five years have passed since the causative gene for familial Parkinson's disease (PD), Parkin (now PRKN), was identified in 1998; PRKN is the most common causative gene in young-onset PD. Parkin encodes a ubiquitin-protein ligase, and Parkin is involved in mitophagy, a type of macroautophagy, in concert with PTEN-induced kinase 1 (PINK1). Both gene products are also involved in mitochondrial quality control. Among the many genetic PD-causing genes discovered, discovering PRKN as a cause of juvenile-onset PD has significantly impacted other neurodegenerative disorders. This is because the involvement of proteolytic systems has been suggested as a common mechanism in neurodegenerative diseases in which inclusion body formation is observed. The discovery of the participation of PRKN in PD has brought attention to the involvement of the proteolytic system in neurodegenerative diseases. Our research group has successfully isolated and identified CHCHD2, which is involved in the mitochondrial electron transfer system, and prosaposin (PSAP), which is involved in the lysosomal system, in this Parkin mechanism. Hereditary PD is undoubtedly an essential clue to solitary PD, and at least 25 or so genes and loci have been reported so far. This number of genes indicates that PD is a very diverse group of diseases. Currently, the diagnosis of PD is based on clinical symptoms and imaging studies. Although highly accurate diagnostic criteria have been published, early diagnosis is becoming increasingly important in treatment strategies for neurodegenerative diseases. Here, we also describe biomarkers that our group is working on.

Comprehensive molecular characterization of adenoid cystic carcinoma reveals tumor suppressors as novel drivers and prognostic biomarkers.

Adenoid cystic carcinoma (ACC) is a MYB-driven head and neck malignancy with high rates of local recurrence and distant metastasis and poor long-term survival. New effective targeted therapies and clinically useful biomarkers for patient stratification are needed to improve ACC patient survival. Here, we present an integrated copy number and transcriptomic analysis of ACC to identify novel driver genes and prognostic biomarkers. A total of 598 ACCs were studied. Clinical follow-up was available from 366 patients, the largest cohort analyzed to date. Copy number losses of 1p36 (70/492; 14%) and of the tumor suppressor gene PARK2 (6q26) (85/343; 25%) were prognostic biomarkers; patients with concurrent losses (n = 20) had significantly shorter overall survival (OS) than those with one or no deletions (p < 0.0001). Deletion of 1p36 independently predicted short OS in multivariate analysis (p = 0.02). Two pro-apoptotic genes, TP73 and KIF1B, were identified as putative 1p36 tumor suppressor genes whose reduced expression was associated with poor survival and increased resistance to apoptosis. PARK2 expression was markedly reduced in tumors with 6q deletions, and PARK2 knockdown increased spherogenesis and decreased apoptosis, indicating that PARK2 is a tumor suppressor in ACC. Moreover, analysis of the global gene expression pattern in 30 ACCs revealed a transcriptomic signature associated with short OS, multiple copy number alterations including 1p36 deletions, and reduced expression of TP73. Taken together, the results indicate that TP73 and PARK2 are novel putative tumor suppressor genes and potential prognostic biomarkers in ACC. Our studies provide new important insights into the pathogenesis of ACC. The results have important implications for biomarker-driven stratification of patients in clinical trials. © 2023 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Managing risky assets - mitophagy in vivo.

Mitochondria, which resemble their α-proteobacteria ancestors, are a major cellular asset, producing energy 'on the cheap' through oxidative phosphorylation. They are also a liability. Increased oxidative phosphorylation means increased oxidative stress, and damaged mitochondria incite inflammation through release of their bacteria-like macromolecules. Mitophagy (the selective macroautophagy of mitochondria) controls mitochondria quality and number to manage these risky assets. Parkin, BNIP3 and NIX were identified as being part of the first mitophagy pathways identified in mammals over a decade ago, with additional pathways, including that mediated by FUNDC1 reported more recently. Loss of Parkin or PINK1 function causes Parkinson's disease, highlighting the importance of mitophagy as a quality control mechanism in the brain. Additionally, mitophagy is induced in idiopathic Parkinson's disease and Alzheimer's disease, protects the heart and other organs against energy stress and lipotoxicity, regulates metabolism by controlling mitochondrial number in brown and beige fat, and clears mitochondria during terminal differentiation of glycolytic cells, such as red blood cells and neurons. Despite its importance in disease, mitophagy is likely dispensable under physiological conditions. This Review explores the in vivo roles of mitophagy in mammalian systems, focusing on the best studied examples - mitophagy in neurodegeneration, cardiomyopathy, metabolism, and red blood cell development - to draw out common themes.

Long-Read Sequencing Resolves a Complex Structural Variant in PRKN Parkinson's Disease.

BACKGROUND: Parkin RBR E3 ubiquitin-protein ligase (PRKN) mutations are the most common cause of young onset and autosomal recessive Parkinson's disease (PD). PRKN is located in FRA6E, which is one of the common fragile sites in the human genome, making this region prone to structural variants. However, complex structural variants such as inversions of PRKN are seldom reported, suggesting that there are potentially unrevealed complex pathogenic PRKN structural variants. OBJECTIVES: To identify complex structural variants in PRKN using long-read sequencing. METHODS: We investigated the genetic cause of monozygotic twins presenting with a young onset dystonia-parkinsonism using targeted sequencing, whole exome sequencing, multiple ligation probe amplification, and long-read sequencing. We assessed the presence and frequency of complex inversions overlapping PRKN using whole-genome sequencing data of Accelerating Medicines Partnership Parkinson's disease (AMP-PD) and United Kingdom (UK)-Biobank datasets. RESULTS: Multiple ligation probe amplification identified a heterozygous exon three deletion in PRKN and long-read sequencing identified a large novel inversion spanning over 7 Mb, including a large part of the coding DNA sequence of PRKN. We could diagnose the affected subjects as compound heterozygous carriers of PRKN. We analyzed whole genome sequencing data of 43,538 participants of the UK-Biobank and 4941 participants of the AMP-PD datasets. Nine inversions in the UK-Biobank and two in AMP PD were identified and were considered potentially damaging and likely to affect PRKN expression. CONCLUSIONS: This is the first report describing a large 7 Mb inversion involving breakpoints outside of PRKN. This study highlights the importance of using long-read sequencing for structural variant analysis in unresolved young-onset PD cases. © 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA.

Heterozygous PRKN mutations are common but do not increase the risk of Parkinson's disease.

PRKN mutations are the most common recessive cause of Parkinson's disease and are a promising target for gene and cell replacement therapies. Identification of biallelic PRKN patients at the population scale, however, remains a challenge, as roughly half are copy number variants and many single nucleotide polymorphisms are of unclear significance. Additionally, the true prevalence and disease risk associated with heterozygous PRKN mutations is unclear, as a comprehensive assessment of PRKN mutations has not been performed at a population scale. To address these challenges, we evaluated PRKN mutations in two cohorts with near complete genotyping of both single nucleotide polymorphisms and copy number variants: the NIH-PD + AMP-PD cohort, the largest Parkinson's disease case-control cohort with whole genome sequencing data from 4094 participants, and the UK Biobank, the largest cohort study with whole exome sequencing and genotyping array data from 200 606 participants. Using the NIH-PD participants, who were genotyped using whole genome sequencing, genotyping array, and multi-plex ligation-dependent probe amplification, we validated genotyping array for the detection of copy number variants. Additionally, in the NIH-PD cohort, functional assays of patient fibroblasts resolved variants of unclear significance in biallelic carriers and suggested that cryptic loss of function variants in monoallelic carriers are not a substantial confounder for association studies. In the UK Biobank, we identified 2692 PRKN copy number variants from genotyping array data from nearly half a million participants (the largest collection to date). Deletions or duplications involving exon 2 accounted for roughly half of all copy number variants and the vast majority (88%) involved exons 2, 3, or 4. In the UK Biobank, we found a pathogenic PRKN mutation in 1.8% of participants and two mutations in ∼1/7800 participants. Those with one PRKN pathogenic variant were as likely as non-carriers to have Parkinson's disease [odds ratio = 0.91 (0.58-1.38), P-value 0.76] or a parent with Parkinson's disease [odds ratio = 1.12 (0.94-1.31), P-value = 0.19]. Similarly, those in the NIH-PD + AMP + PD cohort with one PRKN pathogenic variant were as likely as non-carriers to have Parkinson's disease [odds ratio = 1.29 (0.74-2.38), P-value = 0.43]. Together our results demonstrate that heterozygous pathogenic PRKN mutations are common in the population but do not increase the risk of Parkinson's disease.

Low expression of PINK1 and PARK2 predicts poor prognosis in patients with esophageal squamous cell carcinoma.

BACKGROUND: The Parkinson's disease (PD) gene family expression is strongly linked to tumor development and progression; PINK1 and PARK2 are essential members of the PD gene family. However, the relationship between PINK1 and PARK2 and esophageal squamous cell carcinoma (ESCC) remains unknown. This research aims to clarify the prognostic value of PINK1 and PARK2 in ESCC. METHODS: PINK1 and PARK2 protein levels in 232 ESCC specimens, and 125 matched adjacent normal tissues were detected by immunohistochemistry. The relationship between PINK1 and PARK2 protein expression and clinicopathological features were analyzed. Kaplan-Meier survival analysis was performed to estimate the prognostic value of the PINK1 and PARK2 proteins in patients. Cox univariate and multivariate analyses were used to assess the risk factors affecting the OS for patients with ESCC. RESULTS: PINK1 and PARK2 had low expression in ESCC. Patients with low PINK1 had worse differentiation and advanced T and TNM stages. Lower PARK2 expression was linked to lymph node metastases and an advanced TNM stage. Furthermore, reduced PINK1 and PARK2 levels were associated with a poor prognosis for ESCC. Cox univariate and multivariate analyses revealed that PINK1, PARK2, and tumor size were closely associated with the prognosis of patients with ESCC, and PARK2 was an independent risk factor for patients with ESCC. Finally, the PINK1 and PARK2 proteins were closely related and shared the same signal pathway. CONCLUSIONS: PINK1 and PARK2 could work as tumor suppressors in ESCC and are likely to become new treatment targets for ESCC.

Glial Cultures Differentiated from iPSCs of Patients with PARK2-Associated Parkinson's Disease Demonstrate a Pro-Inflammatory Shift and Reduced Response to TNFα Stimulation.

Parkinson's disease (PD) is the second most common neurodegenerative diseases characterized by progressive loss of midbrain dopaminergic neurons in the substantia nigra. Mutations in the PARK2 gene are a frequent cause of familial forms of PD. Sustained chronic neuroinflammation in the central nervous system makes a significant contribution to neurodegeneration events. In response to inflammatory factors produced by activated microglia, astrocytes change their transcriptional programs and secretion profiles, thus acting as immunocompetent cells. Here, we investigated iPSC-derived glial cell cultures obtained from healthy donors (HD) and from PD patients with PARK2 mutations in resting state and upon stimulation by TNFα. The non-stimulated glia of PD patients demonstrated higher IL1B and IL6 expression levels and increased IL6 protein synthesis, while BDNF and GDNF expression was down-regulated when compared to that of the glial cells of HDs. In the presence of TNFα, all of the glial cultures displayed a multiplied expression of genes encoding inflammatory cytokines: TNFA, IL1B, and IL6, as well as IL6 protein synthesis, although PD glia responded to TNFα stimulation less strongly than HD glia. Our results demonstrated a pro-inflammatory shift, a suppression of the neuroprotective gene program, and some depletion of reactivity to TNFα in PARK2-deficient glia compared to glial cells of HDs.

Manganese Intoxication Recovery and the Expression Changes of Park2/Parkin in Rats.

Occupational overexposure to manganese (Mn) produces Parkinson's disease-like manganism. Acute Mn intoxication in rats causes dopaminergic neuron loss, impairment of motor activity and reduction of the expression of Park2/Parkin. The expression of Park2/Parkin is also reduced. Whether these changes are reversible after cessation of Mn exposure is unknown, and is the goal of this investigation. Adult male rats were injected with Mn2+ at doses 1 mg/kg and 5 mg/kg in the form of MnCl2·4H2O, every other day for one-month to produce acute Mn neurotoxicity. For a half of rats Mn exposure was suspended for recovery for up to 5 months. Mn neurotoxicity was evaluated by the accumulation of Mn in blood and brain, behavioral activities, dopaminergic neuron loss, and the expression of Park2/Parkin in the blood cells and brain. Dose-dependent Mn neurotoxicity in rats was evidenced by Mn accumulation, rotarod impairments, reduction of tyrosine hydroxylase (TH)-positive neurons in the substantia nigra, decreased level of Park2 mRNA in the blood and brain, and decreased Parkin protein in the brain. After cessation of Mn exposure, the amount of Park2 mRNA in the blood started to increase one month after the recovery. After 5-month of recovery, blood and brain Mn returned to normal, rotarod activity recovered, the reduction of TH-positive dopaminergic neurons ameliorated, and the level of Park2 mRNA in the blood and Park2/Parkin in the midbrain and striatum were returned to the normal. Mn neurotoxicity in rats is reversible after cessation of Mn exposure. The level of Park2 mRNA in the blood could be used as a novel biomarker for Mn exposure and recovery.

Rhus Coriaria L. Extract: Antioxidant Effect and Modulation of Bioenergetic Capacity in Fibroblasts from Parkinson's Disease Patients and THP-1 Macrophages.

Sumac, Rhus coriaria L., is a Mediterranean plant showing several useful properties, such as antioxidant and neuroprotective effects. Currently, there is no evidence about its possible neuroprotective action in Parkinson's disease (PD). We hypothesized that sumac could modulate mitochondrial functionality in fibroblasts of familial early-onset PD patients showing PARK2 mutations. Sumac extract volatile profile, polyphenolic content and antioxidant activity have been previously characterized. We evaluated ROS and ATP levels on sumac-treated patients' and healthy control fibroblasts. In PD fibroblasts, all treatments were effective in reducing H2O2 levels, while patients' ATP content was modulated differently, probably due to the varying mutations in the PARK2 gene found in individual patients which are also involved in different mitochondrial phenotypes. We also investigated the effect of sumac extract on THP-1-differentiated macrophages, which show different embryogenic origin with respect to fibroblasts. In THP-1 macrophages, sumac treatment determined a reduction in H2O2 levels and an increase in the mitochondrial ATP content in M1, assuming that sumac could polarize the M1 to M2 phenotype, as demonstrated with other food-derived compounds rich in polyphenols. In conclusion, Rhus coriaria L. extracts could represent a potential nutraceutical approach to PD.

ADHD-associated PARK2 copy number variants: A pilot study on gene expression and effects of supplementary deprivation in patient-derived cell lines.

Recent studies show an association of Parkin RBR E3 ubiquitin protein ligase (PARK2) copy number variations (CNVs) with attention deficit hyperactivity disorder (ADHD). The aim of our pilot study to investigate gene expression associated with PARK2 CNVs in human-derived cellular models. We investigated gene expression in fibroblasts, hiPSC and dopaminergic neurons (DNs) of ADHD PARK2 deletion and duplication carriers by qRT PCR compared with healthy and ADHD cell lines without PARK2 CNVs. The selected 10 genes of interest were associated with oxidative stress response (TP53, NQO1, and NFE2L2), ubiquitin pathway (UBE3A, UBB, UBC, and ATXN3) and with a function in mitochondrial quality control (PINK1, MFN2, and ATG5). Additionally, an exploratory RNA bulk sequencing analysis in DNs was conducted. Nutrient deprivation as a supplementary deprivation stress paradigm was used to enhance potential genotype effects. At baseline, in fibroblasts, hiPSC, and DNs, there was no significant difference in gene expression after correction for multiple testing. After nutrient deprivation in fibroblasts NAD(P)H-quinone-dehydrogenase 1 (NQO1) expression was significantly increased in PARK2 CNV carriers. In a multivariate analysis, ubiquitin C (UBC) was significantly upregulated in fibroblasts of PARK2 CNV carriers. RNA sequencing analysis of DNs showed the strongest significant differential regulation in Neurontin (NNAT) at baseline and after nutrient deprivation. Our preliminary results suggest differential gene expression in pathways associated with oxidative stress, ubiquitine-proteasome, immunity, inflammation, cell growth, and differentiation, excitation/inhibition modulation, and energy metabolism in PARK2 CNV carriers compared to wildtype healthy controls and ADHD patients.

Ascorbate uptake enables tubular mitophagy to prevent septic AKI by PINK1-PARK2 axis.

Ascorbate (Vitamin C) has been proposed as a promising therapeutic agent against sepsis in clinical trials, but there is little experimental evidence on its anti-septic efficacy. We report that Toll-like receptor 4 (TLR4) activation by LPS stimuli augments ascorbate uptake in murine and human tubular cells through upregulation of two ascorbate transporters SVCT-1 and -2 mediated by Fn14/SCFFbxw7α cascade. Ascorbate restriction, or knockout of SVCT-1 and -2, the circumstance reminiscent to blockade of ascorbate uptake, endows tubular cells more vulnerable to the LPS-inducible apoptosis, whereas exogenous administration of ascorbate overrides the ruin execution, for which the PINK1-PARK2, rather than BNIP3-NIX axis is required. Ascorbate increases, while SVCT-1 and -2 knockout or ascorbate restriction dampens tubular mitophagy upon LPS stimuli. Treatment of endotoxemic mice with high-dose ascorbate confers mitophagy and substantial protection against mortality and septic acute kidney injury (AKI). Our work provides a rationale for clinical management of septic AKI with high doses of ascorbate.

Age-associated insolubility of parkin in human midbrain is linked to redox balance and sequestration of reactive dopamine metabolites.

The mechanisms by which parkin protects the adult human brain from Parkinson disease remain incompletely understood. We hypothesized that parkin cysteines participate in redox reactions and that these are reflected in its posttranslational modifications. We found that in post mortem human brain, including in the Substantia nigra, parkin is largely insoluble after age 40 years; this transition is linked to its oxidation, such as at residues Cys95 and Cys253. In mice, oxidative stress induces posttranslational modifications of parkin cysteines that lower its solubility in vivo. Similarly, oxidation of recombinant parkin by hydrogen peroxide (H2O2) promotes its insolubility and aggregate formation, and in exchange leads to the reduction of H2O2. This thiol-based redox activity is diminished by parkin point mutants, e.g., p.C431F and p.G328E. In prkn-null mice, H2O2 levels are increased under oxidative stress conditions, such as acutely by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine toxin exposure or chronically due to a second, genetic hit; H2O2 levels are also significantly increased in parkin-deficient human brain. In dopamine toxicity studies, wild-type parkin, but not disease-linked mutants, protects human dopaminergic cells, in part through lowering H2O2. Parkin also neutralizes reactive, electrophilic dopamine metabolites via adduct formation, which occurs foremost at the primate-specific residue Cys95. Further, wild-type but not p.C95A-mutant parkin augments melanin formation in vitro. By probing sections of adult, human midbrain from control individuals with epitope-mapped, monoclonal antibodies, we found specific and robust parkin reactivity that co-localizes with neuromelanin pigment, frequently within LAMP-3/CD63+ lysosomes. We conclude that oxidative modifications of parkin cysteines are associated with protective outcomes, which include the reduction of H2O2, conjugation of reactive dopamine metabolites, sequestration of radicals within insoluble aggregates, and increased melanin formation. The loss of these complementary redox effects may augment oxidative stress during ageing in dopamine-producing cells of mutant PRKN allele carriers, thereby enhancing the risk of Parkinson's-linked neurodegeneration.

Genetic Variations and Neuropathologic Features of Patients with PRKN Mutations.

BACKGROUND: Mutations in PRKN are the most common cause of autosomal recessive juvenile parkinsonism. The objective of this study was to investigate the association between genotype and pathology in patients with PRKN mutations. METHODS: We performed a sequence and copy number variation analysis of PRKN, mRNA transcripts, Parkin protein expression, and neuropathology in 8 autopsied patients. RESULTS: All the patients harbored biallelic PRKN mutations. Two patients were homozygous and heterozygous, respectively, for the missense mutation p.C431F. Seven patients had exon rearrangements, including 2 patients from a single family who harbored a homozygous deletion of exon 4, and 3 patients who carried a homozygous duplication of exons 6-7, a homozygous duplication of exons 10-11, and a heterozygous duplication of exons 2-4. In the other 2 patients, we found a compound heterozygous duplication of exon 2, deletion of exon 3, and a heterozygous duplication of exon 2. However, sequencing of cDNA prepared from mRNA revealed 2 different transcripts derived from triplication of exon 2 and deletion of exons 2-3 and from duplication of exons 2-4 and deletion of exons 3-4. Western blotting and immunohistochemistry revealed faint or no expression of Parkin in their brains. In the substantia nigra pars compacta, a subfield-specific pattern of neuronal loss and mild gliosis were evident. Lewy bodies were found in 3 patients. Peripheral sensory neuronopathy was a feature. CONCLUSIONS: Genomic and mRNA analysis is needed to identify the PRKN mutations. Variable mutations may result in no or little production of mature Parkin and the histopathologic features may be similar. © 2021 International Parkinson and Movement Disorder Society.

Whole exome sequencing in familial isolated primary hyperparathyroidism.

PURPOSE: Familial isolated hyperparathyroidism (FIHP) is a rare inherited disease accounting for 1% of all cases of primary hyperparathyroidism (PHPT). It is genetically heterogeneous being associated with mutations in different genes, including MEN1, CDC73, CASR, and recently GCM2. The aim of the study was to further investigate the molecular pathogenesis in Italian FIHP kindreds. METHODS: We used whole exome sequencing (WES) in the probands of seven unrelated FIHP kindreds. We carried out a separate family-based exome analysis in a large family characterized by the co-occurrence of PHPT with multiple tumors apparently unrelated to the disease. Selected variants were also screened in 18 additional FIHP kindreds. The clinical, biochemical, and pathological characteristics of the families were also investigated. RESULTS: Three different variants in GCM2 gene were found in two families, but only one (p.Tyr394Ser), already been shown to be pathogenic in vitro, segregated with the disease. Six probands carried seven heterozygous missense mutations segregating with the disease in the FAT3, PARK2, HDAC4, ITPR2 and TBCE genes. A genetic variant in the APC gene co-segregating with PHPT (p.Val530Ala) was detected in a family whose affected relatives had additional tumors, including colonic polyposis. CONCLUSION: We confirm the role of GCM2 germline mutations in the pathogenesis of FIHP, although at a lower rate than in the previous WES study. Further studies are needed to establish the prevalence and the role in the predisposition to FIHP of the novel variants in additional genes.

The Role of Alpha-Synuclein and Other Parkinson's Genes in Neurodevelopmental and Neurodegenerative Disorders.

Neurodevelopmental and late-onset neurodegenerative disorders present as separate entities that are clinically and neuropathologically quite distinct. However, recent evidence has highlighted surprising commonalities and converging features at the clinical, genomic, and molecular level between these two disease spectra. This is particularly striking in the context of autism spectrum disorder (ASD) and Parkinson's disease (PD). Genetic causes and risk factors play a central role in disease pathophysiology and enable the identification of overlapping mechanisms and pathways. Here, we focus on clinico-genetic studies of causal variants and overlapping clinical and cellular features of ASD and PD. Several genes and genomic regions were selected for our review, including SNCA (alpha-synuclein), PARK2 (parkin RBR E3 ubiquitin protein ligase), chromosome 22q11 deletion/DiGeorge region, and FMR1 (fragile X mental retardation 1) repeat expansion, which influence the development of both ASD and PD, with converging features related to synaptic function and neurogenesis. Both PD and ASD display alterations and impairments at the synaptic level, representing early and key disease phenotypes, which support the hypothesis of converging mechanisms between the two types of diseases. Therefore, understanding the underlying molecular mechanisms might inform on common targets and therapeutic approaches. We propose to re-conceptualize how we understand these disorders and provide a new angle into disease targets and mechanisms linking neurodevelopmental disorders and neurodegeneration.

Parkin gene mutations are not common, but its epigenetic inactivation is a frequent event and predicts poor survival in advanced breast cancer patients.

BACKGROUND: Progression of breast cancer involves both genetic and epigenetic factors. Parkin gene has been identified as a tumor suppressor gene in the pathogenesis of various cancers. Nevertheless, the putative role of Parkin in breast cancer remains largely unknown. Therefore, we evaluated the regulation of Parkin through both genetic and epigenetic mechanisms in breast carcinoma. METHOD: A total of 156 breast carcinoma and their normal adjacent tissue samples were included for mutational analysis through SSCP, and sequencing. MS-PCR was employed for methylation study whereas Parkin protein expression was evaluated using immunohistochemistry and western blotting. For the survival analysis, Kaplan-Meier curve and Cox's proportional hazard model were used. RESULTS: In expression analysis, Parkin protein expression was found to be absent in 68% cases of breast cancer. We found that aberrant promoter methylation of Parkin gene is a frequent incident in breast cancer tumors and cell lines. Our MS-PCR result showed that Parkin promoter methylation has a significant role (p = 0.0001) in reducing the expression of Parkin protein. Consistently, expression of Parkin was rectified by treatment with 5-aza-2-deoxycytidine. We also found significant associations of both Parkin negative expression and Parkin promoter methylation with the clinical variables. Furthermore, we found a very low frequency (5.7%) of Parkin mutation with no clinical significance. In survival analysis, patients having Parkin methylation and Parkin loss had a worse outcome compared to those harboring none of these events. CONCLUSION: Overall, these results suggested that promoter methylation-mediated loss of Parkin expression could be used as a prognostic marker for the survival of breast cancer.

Genotype-Phenotype Relations for the Parkinson's Disease Genes Parkin, PINK1, DJ1: MDSGene Systematic Review.

This first comprehensive MDSGene review is devoted to the 3 autosomal recessive Parkinson's disease forms: PARK-Parkin, PARK-PINK1, and PARK-DJ1. It followed MDSGene's standardized data extraction protocol and screened a total of 3652 citations and is based on fully curated phenotypic and genotypic data on >1100 patients with recessively inherited PD because of 221 different disease-causing mutations in Parkin, PINK1, or DJ1. All these data are also available in an easily searchable online database (www.mdsgene.org), which also provides descriptive summary statistics on phenotypic and genetic data. Despite the high degree of missingness of phenotypic features and unsystematic reporting of genotype data in the original literature, the present review recapitulates many of the previously described findings including early onset (median age at onset of ∼30 years for carriers of at least 2 mutations in any of the 3 genes) of an overall clinically typical form of PD with excellent treatment response, dystonia and dyskinesia being relatively common and cognitive decline relatively uncommon. However, when comparing actual data with common expert knowledge in previously published reviews, we detected several discrepancies. We conclude that systematic reporting of phenotypes is a pressing need in light of increasingly available molecular genetic testing and the emergence of first gene-specific therapies entering clinical trials. © 2018 International Parkinson and Movement Disorder Society.